Hi Jesper

Using the approach from iNETZO works, however in my test in removing allowed templates on a document type and re-publish the node, it still had the a value in TemplateAlias and TemplateId. So you might want and additional check on AllowedTemplates:

// Check if the node has an template
if (string.IsNullOrEmpty(e.Model.TemplateAlias) || e.Model.AllowedTemplates.Count == 0)
{
    // Remove the ContentApp by Alias
    e.Model.ContentApps = e.Model.ContentApps.Where(x => x.Alias != "YourContentAppAlias");
}

However since you mention "I would like hide my content app" I guess you have control over how the content app is registered, so instead of removing in afterwards you could add some additional checks here:

public class WordCounterApp : IContentAppFactory
{
    public ContentApp GetContentAppFor(object source, IEnumerable<IReadOnlyUserGroup> userGroups)
    {
        // Can implement some logic with userGroups if needed
        // Allowing us to display the content app with some restrictions for certain groups
        if (userGroups.All(x => x.Alias.ToLowerInvariant() != Umbraco.Core.Constants.Security.AdminGroupAlias))
            return null;

        // only show app on content items
        if (!(source is IContent))
        {
            return null;
        }

        var content = ((IContent)source);

        // only show app on content items with template
        if (content.TemplateId == null)
        {
            return null;
        }

        var myContentApp = new ContentApp
        {
            Alias = "myContentApp",
            Name = "My Content App",
            Icon = "icon-calculator",
            View = "/App_Plugins/MyContentApp/app.html",
            Weight = 0
        };

        return myContentApp;
    }
}

/Bjarne